(a) State Kirchhoffs laws. [2] (b) Using diagrams and equations, show that Kirchhost laws are following: 1') Conservation of Charge Law. it) Conservation of Energy Law. [4] (c) For the circuit shown in Figure 2.1, the internal resistance of each battery is 1.09. 20V 12V 19 H2 20.12 10.9 Figure 2.1 Find: 1') the current owing in each branch of the circuit. it) the terminal p.d. across each battery. iii) the rate at which energy is dissipated in the 209 resistor. [14] 3. (a) Define magnetic flux density and magnetic flux. [2] (b) Sketch the magnetic field pattern surrounding an isolated solenoid carrying a current I. [3] (c) An apprentice sets up the circuit shown in Figure 3.1 to study the magnetic flux density B inside a solenoid. The magnetic probe was placed inside the solenoid to take direct reading of the flux density for various currents I. A set of results are given in the table below. Solenoid Magnetic Probe Figure 3.1 B 0 120 240 360 480 600 720 840 960 1080 (mT) I (A) 0 50 100 150 200 250 300 350 400 450 Plot a graph of B vs I on the graph paper in the back of your answer booklet. ii) What is the relationship between B and I from the plotted graph? iii) Find the gradient of your graph. iv) Using B = Honl for the magnetic flux density inside the solenoid, where n is the number of turns per unit length. Find the constant wo if n = 1100 turns per meter. [15]SECTION A: ELECTRICITY & MAGNETISM Assume where necessary: Acceleration due to gravity, g = 10 ms-2 k = =9.0 x 109N m2C-2 4 TIE Charge on electron = -1.6 x 10-19c Mass of electron in kg =9.1 x 10-31kg Mass of proton = 1.00728 u Mass of neutron = 1.00867 u Mass of - H nucleus = 2.01355 u Mass of H nucleus = 3.01550 u Mass of , He nucleus = 4.00161 u I u = 931 MeV Avogadro's constant, NA =6.02 x 1023 mol-1 PLEASE TURN OVER2 E l NA: ELE TR] [TY MA NETI M (a) Two isolated point charges, +5C and +1 031C are arranged as shown in Figure 1.1. Figure 1.1 1) Determine the point P, where a third charge can be positioned so that it is in equilibrium with the two point charges. it) What are the electric eld strength and the electric potential at P? [8] (b) Figure 1.2 shows the arrangement of four capacitors across a 12V battery. -F I 1 LJ_T Figure 1.2 Find 1) the effective capacitance of the arrangement. ii) the charge stored in each of the capacitors. iii) the potential difference across each capacitor iv) the total energy stored by the four capacitors. [12]